Vulcanizable elastomeric composition comprising natural or synthetic rubber, sulfur and an accelerator



United States Patent 3,236,822 VULCANIZABLE ELASTOMERIC COIVHOSITION CUMPRHSING NATURAL 0R SYNTHETIC RUB- BER, SULFUR AND AN ACCELERATOR Lawrence 15. Sonnahend and George B. Sterling, Midland,

Mich, assignors to The Dow Chemical Company, Midland, Mich, a corporation of Delaware No Drawing. Filed Mar. 5, 1962, Ser. No. 177,241 9 Claims. (Cl. 260-795) This invention relates to certain new vulcanization accelerators and to their use in the manufacture of articles of vulcanizable elastomers.

According to the invention, a vulcanizable elastomeric composition is vulcanized in the presence of a material corresponding to the formula wherein X has a numerical value of from 1 to about 4.

Such mercapatans are readily prepared from the product of the halomethylation of diphenyl oxide by reaction of the said product with an alkali metal sulfhydrate. The reaction involving the exchange of the sulfhydryl group for the halogen of the halomethylated diphenyl oxide is essentially quantitative. However, the halornethylation of the diphenyl oxide does not readily proceed past the point of the introduction of four halomethyl groups into a molecule of the diphenyl oxide. Accordingly, the number of mercaptomethyl groups in a molecule of the vulcanization accelerator is not generally in excess of four. Furthermore, since the halomethylation reaction ordinarily gives rise to a mixture of products containing from one to four halomethyl groups, the value of X in the above formula will be intermediate between 1 and 4, it being impractically diificult and unnecessary to separate the various components resulting from the halomethylation reaction or from the reaction of the mixture of halomethylated compounds with the alkali metal sulfhydrate.

The vulcanization accelerator compositions of the present invention may be used to vulcanize natural and vulcanizable synthetic rubbers which are susceptible to curing when heated with sulfur. They will generally be employed in amounts of from about 0.5 to about 5 percent, based on the weight of the rubber. The vulcanizable composition may, and generally will, contain other compounding ingredients such as fillers, antioxidants, retarders, anti-scorch agents, softeners, pigments and the like.

The elastomeric vulcanizates resulting from the use of the accelerator compositions of the present invention are, in general, characterized by their relatively high elongation.

The invention is illustrated by the following non-limiting examples, showing the preparation of the accelerator compositions and the mode of their employment, in which all parts and percentages are given on a weight basis.

EXAMPLE 1 Into a reaction flask fitted with a condenser, thermometer and stirring means there was charged a mixture of 525 parts of sodium sulfhydrate and 900 parts of methanol. To this charge there was added, with stirring, during a period of about 3 hours, 589 parts of 4,4- di(ohlorornethyl) diphenyl oxide. During addition the temperature was maintained at approximately 30 C. The ethanol was then substantially removed by distillation at reduced pressure at a temperature of about 50 C. To the reaction mixture there were added 500 parts of toluene. The total mixture was then filtered to remove the by-product sodium chloride and the sodium chloride filter cake was washed twice with 200 parts of toluene. The toluene was removed from the mixture by distillation therefrom at a temperature of 140 C. and a pressure of 20 mm. of mercury. The residual product was a viscous, clear liquid having a sulfur content of 24.4 percent. This value for content of sulfur corresponds to 2 for the value of X in the general formula [E -Gl The product, 4,4-di(mercaptomethyl)diphenyl oxide, is hereinafter referred to as accelerator composition A.

EXAMPLE 2 In a manner comparable to that of Example 1, a number of mercaptomethyl diphenyl oxides were prepared from chloromethylated diphenyl oxides of varying chlorine content. These are listed in Table 1, below.

Table l Accelerator Sulfur Content, Value of X in Percent General Formula 20. 0 l. 5 26. 5 2.3 11. 9 a 0. 20. 1 l. 5

I a Value less than unity since D contained unreacted diphenyl oxide.

EXAMPLE 3 The accelerator compositions above indentified were incorporated into various sulfur-curable elastomeric compounds by conventional milling. The resulting materials were cured and the physical properties of the vulcanizates were determined. The compositions of the mill-blended stocks and physical properties of the vulcanizates are set out in Table II, below, wherein the quantities of the various compounding ingredients are given in parts per parts of elastomer.

Table II Carbon Zinc Stearic Magne- Phenyl Tensile, Elongation, Elastoincr Sulfur Black Oxide Accelerator Acid sium a-Naphthyl Cure p.s.i. percent Oxide Amine A1nerip0l1703 2 40 5 D, 1 50 min., 292 F- 55 1,050 Do 2 4o 5 D, 2- do 118 1,050 2 40 5 D, 3. 245 1,000 2 40 2 D, 5- 795 1,100 2 40 5 E, 1 151 550 2 40 5 E, 2 1, 141 850 2 40 5 E, 1,239 800 2 40 5 E, 2, 215 770 2 40 5 C, 1, 473 500 D 2 40 C, 2, 090 520 Natural Rubber, 2. 7 40 5 155 790 Smoked Sheet.

2. 7 40 5 B, 0. 2 915 560 2. 7 40 5 B, 1. 2 1, 320 500 2.7 40 5 B, 2.0" 2 ,d0 836 490 2 40 5 1 45min., 287 F- 117 600 2 40 5 B, 0. 1 .....110 1,290 670 2 40 5 B, 1. 1 1, 890 570 2 40 5 B, 2. 1 2,050 370 2 30 5 1 4 2 1, 580 (150 2 30 5 A, 1 1 4 2 2, 890 000 2 30 5 A, 2 1 4 2 2, 905 050 2 30 5 A, 3 1 4 2 2, 718 030 2 30 5 C, 1 1 4 2 3,020 650 2 30 5 C, 2 1 4 2 2, 925 650 2 30 5 C, 3 1 4 2 do 2,770 720 2 40 5 Benzothiazyl 3 50 min., 292 F. 2, 000 430 Disulfide, 3. 2 40 5 A, 1.0 1,614 840 2 40 5 A, 2.0 2, 322 710 2 40 5 11,3.0 1, 973 440 Copolymer of 23 parts of styrene and 77 parts of butadiene blended with 25 percent, based on eopolymer weight, of naplithenic oils.

b Copolymer of 26 parts of acrylonitrile and 74 parts of butadiene.

9 Copolyiner of 22.5 parts of styrene and 77.5 parts of butadiene blended with an equal weight of naphthenic oils.

We claim:

1. A process of accelerating the vulcanization of a vulcanizable elastomerio composition consisting essentially of a rubber from the group consisting of natural rubber, rubbery copolymers of butadiene and styrene, rubbery copolymers of butadiene and acrylonitrile and neoprene, comprising incorporating in said composition, prior to vulcanization, sulfur and a compound of the wherein X has an average value of from about 1 to about 4, and vulcanizing said composition.

2. A process of accelerating the vulcanization of a vulcanizable elastomeric composition consisting essentially of a rubber from the group consisting of natural rubber, rubbery copolymers of butadiene and styrene, rubbery copolymers of butadiene and acrylonitrile and neoprene, comprising incorporating in said composition, prior to vulcanization, sulfur and from about 0.5 to about 5 parts per 100 parts of elastomer in the said elastomeric composition of a compound of the formula wherein X has an average value of from about 1 to about 4, and vulcanizing said composition.

3. A process according to claim 2 wherein the elastomeric composition comprises natural rubber.

4. A process according to claim 2 wherein the elastowherein X has an average value of from 1 to about 4, and sulfur.

7. A composition according to claim 6 in which the elastomer is natural rubber.

8. A composition according to claim 6 in which the elastomer is a copolymer of butadiene and styrene.

9. A composition according to claim 6 in which the elastomer is a copolymer of butadiene and acrylonitrile.

References Cited by the Examiner UNITED STATES PATENTS 2,510,567 6/1950 Flory 26079 2,964,502 12/1960 Wheelock 260-79 3,008,916 11/1961 Smith 260-495 3,041,304 6/1962 Gardner 260-79.5

JOSEPH L. SCHOFER, Primary Examiner.

LEON I. BERCOVITZ, Examiner. 

6. A VULCANIZABLE ELASTOMERIC COMPOSITION COMPRISING AN ELASTOMER CONSISTING ESSENTIALLY OF A RUBBER FROM THE GROUP CONSISTING OF NATURAL RUBBER, RUBBERY COPOLYMERS OF BUTADIENE AND STYRENE, RUBBERY COPOLYMERS OF BUTADIENE AND ACRYLONITRILE AND NEOPRENE, FROM ABOUT 0.5 TO ABOUT 5 PARTS PER 100 PARTS OF SAID ELASTOMER OF A COMPOUND OF THE FORMULA 